Technical Differences Between Pipes and Tubes

In the steel manufacturing industry one often hear terms such as steel pipes or steel tubing. To those working in this industry it is often not clear what the difference is between a steel pipe and a tube. After all they’re both just hollow cylinders, so many people think that the word has the exact same meaning. That’s however wrong. There are a couple of key differences between steel tubes and pipes

  • Pipe is sized according to a nominal ID( inside diameter ) while tube is sized according to its OD ( outside diameter ) Another major difference is that pipe is rigid while tubing may be either rigid or flexble.

Tubes

  • Tubes can come in different shapes like square, rectangular and cylindrical. Pipe is always cylindrical or round.
  • While rigid tubes are frequently used in structural applications, copper and brass tubes can be rather flexible. Pipes are typically always rigid and resistant to bending.
  • When it comes to classification, pipes use schedule and nominal diameter. For example, a pipe could have a 250mm nominal diameter and a schedule of 80. Tubes are classified by their outside diameter measurement and thickness. A copper tube, for instance, could be 10 mm with a 2 mm thickness.
  • Pipes accommodate larger applications with sizes that range from a half-inch to several feet. Tubes are generally used in applications that require smaller diameters. While 10-inch pipes are common, it’s rare that you will come across a 10-inch tube.
  • Tubes are often put to use in applications that require precise outside diameters, like with cooler tubes, heat exchanger tubes and boiler tubes.
    Pipes have a pressure rating and are schedule, which is why they are often used to carry fluids that must be contained.
  • The thickness of tubes increases in standard increments such as 1 mm or 2 mm. Pipe thickness depends on the schedule, so there is no fixed increment.
  • Joining pipes is more labor intensive as it requires welding, threading or flanges. Tubes can be joined quickly and easily with flaring, brazing or couplings, but for this reason, they don’t offer the same stability
  • Pipes are used to transport something, and tubes to construct something; hence, tubes are defined by the od “outside diamater” and wt “wall thickness” (for construction stability), and pipes id inside diamater to allow a calculation for transportation viz., speed, volumes etc. (od = id + 2 * wt)

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